Brass alloy as raw materials for semi solid metal casting

ABSTRACT

A brass alloy as raw materials for Semi Solid Metal casting has a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, and a balance of Cu and inevitable impurities, further containing one or more kinds of Si of 2 to 5 mass %, Sn of 0.05 to 6 mass %, and Al of 0.05 to 3.5 mass % as needed, and further containing one or more kinds of Pb of 0.005 to 0.45 mass %, Bi of 0.005 to 0.45 mass %, Se of 0.03 to 0.45 mass %, and Te of 0.01 to 0.45 mass %.

TECHNICAL FIELD

The present invention relates to a brass alloy as raw materials for Semi Solid Metal casting that can be used to produce a brass alloy cast having fine grains by Semi Solid Metal casting (semi-solid alloy casting) without agitating a molten metal.

Priority is claimed on Japanese Patent Application No. 2006-034126, filed Feb. 10, 2006, the content of which is incorporated herein by reference.

BACKGROUND ART

Industrially-used brass contains Zn of 8 mass % to 50 mass % and is classified depending on the usage thereof. Roughly, the brass is classified into a brass alloy containing Zn of 8 mass % to 20 mass % and a balance of Cu and inevitable impurities, a brass alloy containing Zn of 25 mass % to 35 mass % and a balance of Cu and inevitable impurities, and a brass alloy containing Zn of 35 mass % to 45 mass % and a balance of Cu and inevitable impurities. The brass alloy containing Zn of 8 to 20 mass % is used to produce decorations because its color is closest to gold color. A representative of the brass alloy containing Zn of 25 to 35 mass % is the 7-3 brass containing copper of 70 mass % and zinc of 30 mass % and having an even α solid solution structure. A representative of the brass alloy containing Zn of 35 to 45 mass % is the 6-4 brass containing copper of 60 mass % and zinc of 40 mass % and having a α+β solid solution structure. The brass alloys are widely used to produce a variety of mechanical components. A special brass alloy of which the molten alloy flowability is improved by adding Si thereto, a special brass alloy to which Pb, Bi, Se, and Te are added alone or in combinations so as to improve the free machinability, and a special brass alloy to which Al, Fe, Mn, and Ni are added alone or in combinations so as to improve strength, corrosion resistance, and wear resistance are also known.

When the molten metals of the brass alloys are melted and cast by the use of a usual method, a dendrite structure is generated and a brass alloy cast having fine grains is not thus obtained. Accordingly, various casting methods for obtaining a brass alloy cast having fine grains have been suggested and a semi-solid alloy casting method has been suggested as an example thereof. In this casting method, an alloy (where the alloy in a slurry state is referred to as “semi-solid alloy”) in a slurry state in which solid metals and liquid metals are mixed in a temperature range between the liquidus temperature of the alloy and the solidus temperature is cooled and solidified while being agitated mechanically or electromagnetically and the agitation is stopped when a predetermined solid phase ratio is obtained before casting. According to the casting method, the dendrite generated in the solid-liquid mixture slurry is segmentalized by the agitation and the primary crystal solid in the solid-liquid mixture slurry becomes spherical in shape. Accordingly, the flowability can be maintained at a high solid phase ratio. According to the casting method, a brass alloy cast having fine grains can be obtained (see Non-patent Document 1).

[Non-patent Document 1] “Fifth Revised Edition of Metal Manual,” edited by THE JAPAN INSTITUTE OF METALS, MARUZEN Co., Ltd. (published on Apr. 20, 1992), P1041 to P1042

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in executing the semi-solid alloy casting method in which the molten metal is agitated, since it is necessary to perform the agitation under the control of a molten metal temperature, an apparatus needs to be increased in size. Accordingly, superfluous gas may be introduced into the molten metal under some conditions. The molten metal temperature needs to be lowered in consideration of wear damage. However, the generation of the dendrite structure cannot be completely suppressed even when the known brass alloy is agitated in a semi-solid state. Accordingly, the flowability of the molten metal is markedly deteriorated, thereby finally causing casting failure.

The invention is contrived in view of the above-mentioned problems. An object of the invention is to provide a brass alloy as raw materials for Semi Solid Metal casting that can produce a brass alloy cast having fine grains by the use of a semi-solid alloy casting method without using a member for agitating the molten metal.

Means for Solving the Problems

Therefore, the inventors studied in order to enhance the flowability of the semi-solid brass alloy without using a member for segmentalizing and granulating dendrite in a liquid phase and to produce a brass alloy cast having fine grains without casting failure occurring even when the semi-solid brass alloy is cast at a low temperature. As a result, the following (A) to (D) were found.

(A) A semi-solid brass alloy obtained by using a brass alloy, which is obtained by adding Zr of 0.0005 to 0.04 mass % and P of 0.01 to 0.25 mass % to a brass alloy containing Zn of 8 to 40 mass %, as a raw alloy, completely melting the brass alloy into a liquid phase, and cooling the molten brass alloy and a semi-solid brass alloy obtained by re-melting the ingot thereof are both excellent in flowability. Accordingly, it was found that it is possible to produce a brass alloy cast having fine grains by casting the semi-solid brass alloy and that it is not necessary to perform an agitation process in a semi-solid alloy, unlike in known examples.

(B) A semi-solid brass alloy obtained by using a brass alloy, which is obtained by adding one or more kinds of Si of 2 to 5 mass %, Sn of 0.05 mass % to 6 mass %, and Al of 0.05 to 3.5 mass % to the brass alloy according to (A) containing Zr of 0.0005 to 0.04 mass % and P of 0.01 to 0.25 mass %, as a raw alloy, completely melting the brass alloy into a liquid phase, and cooling the molten brass alloy, and a semi-solid brass alloy obtained by re-melting the ingot thereof are both excellent in flowability. Accordingly, it was found that it is possible to produce a brass alloy cast having fine grains by casting the semi-solid brass alloy and that it is not necessary to perform an agitation process in a semi-solid alloy, unlike in known examples.

(C) It was found that a brass alloy further containing one or more kinds of Pb of 0.005 to 0.45 mass %, Bi of 0.005 to 0.45 mass %, Se of 0.03 to 0.45 mass %, and Te of 0.01 to 0.45 mass % in addition to the brass alloy according to (A) or (B) exhibits the same advantages.

(D) It was found that the reason for the excellent flowability in the semi-solid alloy state of the brass alloy according to (A), (B), or (C) is that fine and granular α primary crystals are crystallized instead of dendrite in the course of cooling and solidifying the brass alloy according to (A), (B), or (C) after completely melting the brass alloy and that fine and granular α primary crystals coexist in the liquid phase of the semi-solid brass alloy obtained by re-melting the brass alloy according to (A), (B), or (C).

The invention provides the following based on the above-mentioned results:

(1) A brass alloy as raw materials for Semi Solid Metal casting, having a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, and a balance of Cu and inevitable impurities.

(2) A brass alloy as raw materials for Semi Solid Metal casting, having a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, one or more kinds of Si of 2 to 5 mass %, Sn of 0.05 to 6 mass %, and Al of 0.05 to 3.5 mass %, and a balance of Cu and inevitable impurities.

(3) The brass alloy as raw materials according to (1) or (2) may have the component composition further containing one or more kinds of Pb of 0.005 to 0.45 mass %, Bi of 0.005 to 0.45 mass %, Se of 0.03 to 0.45 mass %, and Te of 0.01 to 0.45 mass

Advantages of the Invention

When the brass alloy as raw materials for Semi Solid Metal casting according to the invention is melted to produce a semi-solid brass alloy in a solid-liquid mixture slurry and the semi-solid brass alloy is cast using a conventional method, a fine and granular α primary phase is generated or an α solid phase coexists in the liquid phase of the semi-solid brass alloy. Accordingly, even when an agitating apparatus is not used, it is possible to cast the semi-solid brass alloy without damaging the flowability of the semi-solid brass alloy. In addition, it is an advantage that the crystal grains of the brass alloy cast obtained by casting the semi-solid brass alloy are further reduced in size, thereby further enhancing the mechanical strength.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the invention will be described in detail.

A brass alloy as raw materials for Semi Solid Metal casting according to the invention has a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, and a balance of Cu and inevitable impurities.

The brass alloy as raw materials for Semi Solid Metal casting according to the invention may have a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, one or more kinds of Si of 2 to 5 mass %, Sn of 0.05 to 6 mass %, and Al of 0.05 to 3.5 mass %, and a balance of Cu and inevitable impurities.

The brass alloy as raw materials for Semi Solid Metal casting according to the invention may have a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, one or more kinds of Si of 2 to 5 mass %, Sn of 0.05 to 6 mass %, and Al of 0.05 to 3.5 mass %, one or more kinds of Pb of 0.005 to 0.45 mass %, Bi of 0.005 to 0.45 mass %, Se of 0.03 to 0.45 mass %, and Te of 0.01 to 0.45 mass %, and a balance of Cu and inevitable impurities.

Ingots of the brass alloy as raw materials for Semi Solid Metal casting according to the invention, the component composition of which is adjusted, may be produced and stored in advance, a semi-solid brass alloy may be produced by re-melting a necessary amount of the ingot of brass alloy as raw materials, and a semi-solid brass alloy cast having fine grains can be manufactured by casting the semi-solid brass alloy.

The reasons for defining the component composition of the brass alloy as raw materials for Semi Solid Metal casting according to the invention as described above will be described.

Zn:

Zn has a function of lowering the melting point, improving the flowability of the molten alloy, and enhancing the corrosion resistance and the mechanical strength of the cast by means of the addition thereof to Cu. When the content thereof is less than 8 mass %, it is not preferable because the flowability of the molten alloy is lowered. On the other hand, when the content thereof is greater than 40 mass %, it is not preferable because the obtained cast is hard and brittle, thus reducing the mechanical strength. Accordingly, the content of Zn contained in the brass alloy as raw materials for Semi Solid Metal casting according to the invention is defined in the range of 8 mass % to 40 mass %.

Zr:

With the coexistence with P, Zr has a function of promoting the generation of fine α primary crystals in a semi-solid alloy state, allowing the α solid phase to coexist in the liquid phase of the semi-solid brass alloy by means of re-melting to improve the flowability of the semi-solid brass alloy, and reducing the size of the crystal grains of the obtained brass alloy cast. When the content thereof is less than 0.0005 mass %, it is not preferable because the reduction in size of the crystal grains of the brass alloy cast is not sufficient. On the other hand, when the content is greater than 0.04 mass %, it is not preferable because the crystal grains of the brass alloy cast rather increase in size. Accordingly, the content of Zr contained in the brass alloy as raw materials for Semi Solid Metal casting according to the invention is defined in the range of 0.0005 mass % to 0.04 mass %.

P:

With the coexistence with Zr, P has a function of promoting the generation of fine α primary crystals in a semi-solid alloy state, allowing the α solid phase to coexist in the liquid phase of the semi-solid brass alloy by means of re-melting to improve the flowability of the semi-solid brass alloy, and reducing the size of the crystal grains of the obtained brass alloy cast. When the content thereof is less than 0.01 mass %, it is not preferable because the reduction in size of the crystal grains of the brass alloy cast is not sufficient. On the other hand, when the content is greater than 0.25 mass %, it is not preferable because the crystal grains of the cast increase in size. Accordingly, the content of P contained in the brass alloy as raw materials for Semi Solid Metal casting according to the invention is defined in the range of 0.01 mass % to 0.25 mass %.

Si, Sn, Al:

When one or more kinds of Si, Sn, and Al are added along with Zr, P, Cu, and Zn, Si, Sn, and Al have a function of improving the mechanical strength, the corrosion resistance, the machinability, and the wear resistance, widening the composition range for a peritectic reaction, and exhibiting the marked effect of reducing the size of the crystal grains. The components are added as needed to further improve the flowability of the semi-solid brass alloy.

In this case, when the content of Si is less than 2 mass %, the desired effect is not obtained. On the other hand, when the content is greater than 5 mass %, it is not preferable because the thermal conductivity is reduced and the flowability of the semi-solid brass alloy is reduced.

Sn has a function of improving the seawater resistance of the corrosion resistance. When the content is less than 0.05 mass %, the desired effect is not obtained. On the other hand, when the content is greater than 6 mass %, it is not preferable because the cast is brittle, the thermal conductivity is lowered, and the flowability of the semi-solid brass is reduced.

Al has a function of improving the flowability of the molten alloy, reducing the loss of Zr, and improving the erosion-corrosion resistance of the corrosion resistance in addition to the above-mentioned functions. When the content is less than 0.05 mass %, the desired effect is not obtained. On the other hand, when the content is greater than 3.5 mass %, it is not preferable because the thermal conductivity is deteriorated and the flowability of the semi-solid brass alloy decreases.

Accordingly, the content of Si contained in the brass alloy as raw materials for Semi Solid Metal casting according to the invention is defined in the range of 2 to 5 mass %, the content of Sn is defined in the range of 0.05 to 6 mass %, and the content of Al is defined in the range of 0.05 to 3.5 mass %. Among the components of Si, Sn, and Al, Si is the most effective and it is most preferable to essentially contain Si.

Other Components:

The brass alloy as raw materials for Semi Solid Metal casting according to the invention may further contain one or more kinds of Pb, Bi, Se, and Te as needed. When the components are contained in the brass alloy, it is preferable that the content of Pb be in the range of 0.005 mass % to 0.45 mass %, the content of Bi be in the range of 0.005 mass % to 0.45 mass %, the content of Se be in the range of 0.03 mass % to 0.45 mass %, and the content of Te be in the range of 0.01 mass % to 0.45 mass %.

By setting the component composition of the brass alloy for Semi Solid Metal casting according to the invention as described above, when the brass alloy as raw materials for Semi Solid Metal casting according to the invention is melted to produce a semi-solid brass alloy in a solid-liquid mixture slurry and the semi-solid brass alloy is cast using a conventional method, a fine and granular α primary phase is generated or an α solid phase coexists in the liquid phase of the semi-solid brass alloy. Accordingly, even when an agitating apparatus is not used, it is possible to cast the semi-solid brass alloy without damaging the flowability of the semi-solid brass alloy. In addition, it is an advantage that the crystal grains of the brass alloy cast obtained by casting the semi-solid brass alloy are further reduced in size, thereby further enhancing the mechanical strength.

EMBODIMENTS Embodiment 1

By preparing usual cathode copper as a raw material, feeding the cathode copper into an electrical furnace, melting the cathode copper in an atmosphere of Ar gas, adding Zn and P thereto when the temperature of molten copper is 1200° C., adding Si, Sn, Al, Pb, Bi, Se, Te, and the like thereto as needed, and finally adding Zr thereto, a molten brass alloy of which the component composition is adjusted was produced. By casting and solidifying the molten brass alloy, ingots of brass alloys as raw materials for Semi Solid Metal casting (hereinafter, referred to as brass alloys as raw materials according to examples of the invention) according to Examples 1 to 105 of the invention and brass alloys as raw materials for Semi Solid Metal casting (hereinafter, referred to as brass alloys as raw materials according to comparative examples) according to Comparative Examples 1 to 8, which have the component compositions shown in Tables 1 to 8, were produced. By melting a 7-3 brass alloy containing copper of 70 and zinc of 30 mass % available on the market and a 6-4 brass alloy containing copper of 60 mass % and zinc of 40 mass % available on the market in an atmosphere of Ar gas, a molten brass alloy of a temperature of 1200° C. was produced. By casting and solidifying the molten brass alloy, ingots of a brass alloy as raw materials for Semi Solid Metal casting (hereinafter, referred to as a known brass alloy as raw materials) according to Conventional Examples 1 and 2 having the component composition shown in Table 7 were produced.

By cutting out parts of the ingots of the brass alloys as raw materials according to Examples 1 to 105, the brass alloys as raw materials according to Comparative Examples 1 to 8, and the brass alloy as raw materials according to Conventional Examples 1 and 2 and heating the cut-out ingots at a predetermined temperature between the solidus temperature and the liquidus temperature to re-melt the ingots, semi-solid brass alloys were produced. Quenched samples were produced by rapidly quenching the semi-solid brass alloys. By observing the structures of the quenched samples with an optical microscope, the shapes of the α solid phase coexisting with the liquid phase in the semi-solid brass alloys were estimated and the average grain sizes thereof were measured. The results are shown in Tables 1 to 8.

The average grain sizes of the α solid phase were measured by etching the cutting surfaces of the quenched samples with nitric acid and then observing the cutting surfaces with the optical microscope.

TABLE 1 α solid phase in quenched sample Brass alloy Average as raw Component composition (mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) The 1 12 0.015 0.08 — — — — balance granular 200 Present 2 16 0.018 0.08 — — — — balance granular 120 Invention 3 20 0.0060 0.07 — — — — balance granular 80 4 24 0.0094 0.05 — — — — balance granular 60 5 30 0.0008 0.09 — — — — balance granular 150 6 34 0.0015 0.11 — — — — balance granular 120 7 36 0.031 0.16 — — — — balance granular 90 8 38 0.028 0.13 — — — — balance granular 120 9 30 0.0005 0.04 — — — — balance granular 200 10 35 0.04 0.23 — — — — balance granular 150 11 20 0.009 0.01 — — — — balance granular 200 12 30 0.009 0.25 — — — — balance granular 200 13 33 0.008 0.06 — — — — balance granular 40 14 31 0.007 0.07 — — — — balance granular 35 15 10 0.0008 0.08 5.0 — — — balance granular 150

TABLE 2 α solid phase in quenched sample Brass alloy Average as raw Component composition (mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) The 16 14 0.0015 0.08 4.0 — — — balance granular 100 Present 17 18 0.0060 0.07 3.4 — — — balance granular 40 Invention 18 22 0.0090 0.05 2.7 — — — balance granular 35 19 26 0.015 0.09 2.2 — — — balance granular 50 20 30 0.018 0.11 2.0 — — — balance granular 100 21 13 0.0005 0.23 4.4 — — — balance granular 200 22 20 0.009 0.01 2.4 — — — balance granular 200 23 25 0.009 0.25 2.1 — — — balance granular 250 24 15 0.008 0.06 4.0 — — — balance granular 45 25 29 0.005 0.02 — 1 — — balance granular 90 26 17 0.02 0.1 — 3.5 — — balance granular 40 27 8 0.009 0.17 — 5.5 — — balance granular 35 28 32 0.007 0.07 — 0.5 — — balance granular 50 29 36 0.005 0.03 — — 0.5 — balance granular 50 30 22 0.003 0.12 — — 2 — balance granular 35

TABLE 3 α solid phase in quenched sample Brass alloy Average as raw Component composition (mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) The 31 17 0.025 0.08 — — 3 — balance granular 60 Present 32 27 0.005 0.05 — 0.8 0.8 — balance granular 45 Invention 33 21 0.008 0.07 — 1.5 0.2 — balance granular 45 34 18 0.002 0.1 3.2 0.1 — — balance granular 35 35 22 0.005 0.02 2.9 0.4 — — balance granular 70 36 22 0.009 0.05 2.4 — 1.2 — balance granular 45 37 14 0.005 0.13 3.8 — 0.1 — balance granular 40 38 19 0.004 0.08 3 0.2 0.4 — balance granular 25 39 12 0.0008 0.08 — — — Pb: 0.019 balance granular 200 40 16 0.0015 0.08 — — — Pb: 0.12 balance granular 150 41 20 0.0060 0.07 — — — Pb: 0.28 balance granular 120 42 24 0.0094 0.05 — — — Pb: 0.38 balance granular 80 43 30 0.015 0.09 — — — Pb: 0.07 balance granular 40 44 34 0.018 0.11 — — — Pb: 0.009 balance granular 50 45 36 0.031 0.16 — — — Pb: 0.30 balance granular 80

TABLE 4 α solid phase in quenched sample Brass alloy Average as raw Component composition (mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) The 46 23 0.0005 0.23 2.75 — — Pb: 0.12 balance granular 200 Present 47 18 0.04 0.04 3.21 — — Pb: 0.28 balance granular 150 Invention 48 20 0.009 0.01 3.18 — — Pb: 0.45 balance granular 150 49 16 0.009 0.25 3.23 — — Pb: 0.07 balance granular 150 50 22 0.008 0.06 2.95 — — Pb: 0.005 balance granular 30 51 12 0.0008 0.08 — — — Bi: 0.019 balance granular 200 52 16 0.0015 0.08 — — — Bi: 0.12 balance granular 150 53 20 0.0060 0.07 — — — Bi: 0.28 balance granular 120 54 24 0.0094 0.05 — — — Bi: 0.38 balance granular 80 55 30 0.015 0.09 — — — Bi: 0.07 balance granular 40 56 34 0.018 0.11 — — — Bi: 0.009 balance granular 50 57 36 0.031 0.16 — — — Bi: 0.30 balance granular 80 58 23 0.0005 0.23 2.75 — — Bi: 0.12 balance granular 200 59 18 0.04 0.04 3.21 — — Bi: 0.28 balance granular 150 60 20 0.009 0.01 3.18 — — Bi: 0.38 balance granular 150

TABLE 5 α solid phase in quenched sample Brass alloy Average as raw Component composition (mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) The 61 16 0.009 0.25 3.23 — — Bi: 0.07 balance granular 150 Present 62 22 0.008 0.06 2.95 — — Bi: 0.009 balance granular 30 Invention 63 12 0.0008 0.08 — — — Se: 0.05 balance granular 200 64 16 0.0015 0.08 — — — Se: 0.45 balance granular 150 65 20 0.0060 0.07 — — — Se: 0.12 balance granular 120 66 24 0.0094 0.05 — — — Se: 0.28 balance granular 80 67 30 0.015 0.09 — — — Se: 0.38 balance granular 40 68 34 0.018 0.11 — — — Se: 0.30 balance granular 50 69 36 0.031 0.16 — — — Se: 0.19 balance granular 80 70 23 0.0005 0.23 2.75 — — Se: 0.33 balance granular 200 71 18 0.04 0.04 3.21 — — Se: 0.28 balance granular 150 72 20 0.009 0.01 3.18 — — Se: 0.38 balance granular 150 73 16 0.009 0.25 3.23 — — Se: 0.45 balance granular 150 74 22 0.008 0.06 2.95 — — Se: 0.03 balance granular 30 75 12 0.0008 0.08 — — — Te: 0.08 balance granular 200

TABLE 6 α solid phase in quenched sample Brass alloy Average as raw Component composition (mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) The 76 16 0.0015 0.08 — — — Te: 0.42 balance granular 150 Present 77 20 0.0060 0.07 — — — Te: 0.21 balance granular 120 Invention 78 24 0.0094 0.05 — — — Te: 0.33 balance granular 80 79 30 0.015 0.09 — — — Te: 0.28 balance granular 40 80 34 0.018 0.11 — — — Te: 0.38 balance granular 50 81 36 0.031 0.16 — — — Te: 0.45 balance granular 80 82 23 0.0005 0.23 2.75 — — Te: 0.12 balance granular 200 83 18 0.04 0.04 3.21 — — Te: 0.28 balance granular 150 84 20 0.009 0.01 3.18 — — Te: 0.38 balance granular 150 85 16 0.009 0.25 3.23 — — Te: 0.30 balance granular 150 86 22 0.008 0.06 2.95 — — Te: 0.19 balance granular 30 87 12 0.0008 0.08 — — — Pb: 0.18, Bi: 0.12 balance granular 200 88 16 0.0015 0.08 — — — Pb: 0.18, Se: 0.12 balance granular 150 89 20 0.0060 0.07 — — — Bi: 0.12, Te: 0.12 balance granular 120 90 24 0.0094 0.05 — — — Bi: 0.18, Te: 0.18 balance granular 80

TABLE 7 α solid phase in quenched sample Brass alloy Average as raw Component composition(mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) The 91 30 0.015 0.09 — — — Pb: 0.18, Bi: 0.12 balance granular 40 Present 92 34 0.018 0.11 — — — Pb: 0.18, Se: 0.12 balance granular 50 Invention 93 36 0.031 0.16 — — — Bi: 0.12, Te: 0.12 balance granular 80 94 23 0.0005 0.23 2.75 — — Pb: 0.18, Bi: 0.12 balance granular 200 95 18 0.04 0.04 3.21 — — Pb: 0.18, Se: 0.12 balance granular 150 96 20 0.009 0.01 3.18 — — Bi: 0.12, Te: 0.12, balance granular 150 Se: 0.12 97 16 0.009 0.25 3.23 — — Bi: 0.18,Te: 0.18 balance granular 150 98 22 0.008 0.06 2.95 — — Pb: 0.18, Te: 0.12 balance granular 30 99 18 0.002 0.1 3.2 0.1 — Pb: 0.18, Se: 0.12 balance granular 35 100 22 0.005 0.02 2.9 0.4 — Bi: 0.12, Te: 0.12 balance granular 70 101 22 0.009 0.05 2.4 — 1.2 Pb: 0.18, Bi: 0.12 balance granular 45 102 17 0.02 0.1 — 3.5 — Pb: 0.18, Se: 0.12 balance granular 40 103 8 0.009 0.17 — 5.5 — Se: 0.12, Te: 0.12, balance granular 35 Pb: 0.11 104 17 0.025 0.08 — — 3 Bi: 0.18, Te: 0.18 balance granular 60 105 27 0.005 0.05 — 0.8 0.8 Pb: 0.18, Te: 0.12 balance granular 45

TABLE 8 α solid phase in quenched sample Brass alloy Average as raw Component composition (mass %) grain size materials Zn Zr P Si Sn Al Pb, Bi, Se, Te Cu shape (μm) Comparative 1  7* 0.005 0.003 — — — — balance dendrite-phase — Example 2  45* 0.005 0.05 — — — — balance dendrite-phase — 3 30 0.0003* — — — — — balance dendrite-phase — 4 25 0.042* — — — — — balance granular 400 5 20 0.01 0.008* — — — — balance dendrite-phase — 6 15 0.01 0.26* — — — — balance dendrite-phase — 7 20 0.01  —* — — — — balance dendrite-phase — 8 25  —* 0.05 — — — — balance dendrite-pahse — Conventional 1 30 — — — — — — balance dendrite-phase — 2 40 — — — — — — balance dendrite-phase — Mark * represents a value departing from the condition of the invention.

It is estimated from the results shown in Tables 1 to 8 that the fine and granular α solid phase coexists with the liquid phase in the semi-solid state of the bronze alloys as raw materials according to Examples 1 to 105, since the α solid phase of the quenched samples are all finely granular. On the other hand, it is estimated that dendrite is generated in the semi-solid state of the brass alloys as raw materials according to Conventional Examples 1 and 2, since the α solid phase of the quenched samples of the brass alloys as raw materials according to Conventional Examples 1 and 2 is in a dendrite phase.

Accordingly, it can be seen that the semi-solid brass alloys produced from the brass alloys as raw materials according to Examples 1 to 105 are better in flowability than the semi-solid brass alloys produced from the brass alloys as raw materials according to Conventional Examples I and 2 and that the fine and granular α solid phase is generated in the liquid phase of the semi-solid brass alloys obtained by melting the brass alloys as raw materials according to Examples 1 to 105, thereby obtaining a cast having fine grains even when the semi-solid brass alloy is cast without agitation. It can be also seen that the brass alloys as raw materials according to Comparative Examples 1 to 6 containing Zn, Zr, and P, which depart from the condition of the invention (the range of component composition of the invention), are not preferable since dendrite is generated, the reduction in size of the crystal grains is insufficient in the semi-solid state thereof or the alloys are brittle and that dendrite is generated in the brass alloys according to Comparative Examples 7 and 8 in which Zr of 0.0005 to 0.04 mass % and P of 0.01 to 0.25 mass % do not coexist and are not contained.

Embodiment 2

By cutting out parts of the ingots of the brass alloys as raw materials according to Examples 1 to 105 produced in Embodiment 1, the brass alloys as raw materials according to Comparative Examples 1 to 8, and the brass alloys as raw materials according to Conventional Examples 1 and 2 and completely melting the cut-out ingots, molten brass alloys in a liquid phase were produced. Semi-solid brass alloys maintained at a predetermined temperature between the solidus temperature and the liquidus temperature were produced by cooling the molten brass alloy thereafter. Quenched samples were produced by rapidly quenching the semi-solid brass alloys. By observing the structures of the quenched samples with an optical microscope, the shapes of the α solid crystals crystallized in the semi-solid brass alloys were estimated and the average grain sizes thereof were measured. The results were the same as Embodiment 1.

INDUSTRIAL APPLICABILITY

When the brass alloy as raw materials for Semi Solid Metal casting according to the invention is melted to produce a semi-solid brass alloy in a solid-liquid mixture slurry and the semi-solid brass alloy is cast using a conventional method, a fine and granular α primary phase is generated or an α solid phase coexists in the liquid phase of the semi-solid brass alloy. Accordingly, even when an agitating apparatus is not used, it is possible to cast the semi-solid brass alloy without damaging the flowability of the semi-solid brass alloy. In addition, it is an advantage that the crystal grains of the brass alloy cast obtained by casting the semi-solid brass alloy are further reduced in size, thereby further enhancing the mechanical strength. Therefore the present invention is useful in industry. 

1. A brass alloy as raw materials for Semi Solid Metal casting, having a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, and a balance of Cu and inevitable impurities.
 2. A brass alloy as raw materials for Semi Solid Metal casting, having a component composition containing Zn of 8 to 40 mass %, Zr of 0.0005 to 0.04 mass %, P of 0.01 to 0.25 mass %, one or more kinds of Si of 2 to 5 mass %, Sn of 0.05 to 6 mass %, and Al of 0.05 to 3.5 mass %, and a balance of Cu and inevitable impurities.
 3. The brass alloy as raw materials according to claim 1, wherein the component composition further contains one or more kinds of Pb of 0.005 to 0.45 mass %, Bi of 0.005 to 0.45 mass %, Se of 0.03 to 0.45 mass %, and Te of 0.01 to 0.45 mass %.
 4. The brass alloy as raw materials according to claim 2, wherein the component composition further contains one or more kinds of Pb of 0.005 to 0.45 mass %, Bi of 0.005 to 0.45 mass %, Se of 0.03 to 0.45 mass %, and Te of 0.01 to 0.45 mass %. 